Sonic borehole televiewer apparatus



8 Sheets-Sheet 1 I I I l l I I I l I l l I I l I l l I I I I l l I I I I I I I I March 24, 1970 J. E. CHAPMAN m SONIC BOREHOLE TELEVIEWER APPARATUS Filed Jan. 15, 1968 March 24, 1970 '.1. E. CHAPMAN m 3,502,169

SONIC BOREHOLE TELEVIEWER APPARATUS 8 Sheets-Sheet 2 Filed Jan. 15, 1968 his ATTORNEYS March 24, 1970 J. E. CHAPMAN m 3,502,169

SONIC BOREHOLE TELEVIEWER APPARATUS 8 Sheets-Sheet :5

Filed Jan. 15, 1968 LEM-...m24

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SONIC BOREHOLE TELEVIEWER APPARATUS 8 Sheets-Sheet '7 FIG. 8

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I IL INVENTOR.

JOSEPH E. CHAPMAN III 5.3.7, FM, 11M/M ArOR/vfrs his nted States Int. Cl. G01v 1/40 U.S. Cl. 181-05 26 Claims ABSTRACT F THE DISCLOSURE As described herein, a borehole Wall is scanned by a rotating instrument, situated within the borehole, which includes a 2 megacycle transducer and a magnetometer. The transducer is rotated to scan the circumference of the borehole and is moved at a selected velocity to provide a record consisting of horizontal circumferential scans over an interval of the well bore. The transducer emits and receives acoustic energy repetitively through each 360 of rotation. A magnetometer is similarly rotated to provide a reference to the direction North for each scan. Signals representative of the intensity of the reected acoustic energy as developed by the transducer are converted into pulses for each transmitted burst of energy and supplied to an intensity input of an oscilloscope located at the surface. The signals developed by the magnetometer are converted into sawtooth voltage signals and supplied to the vertical sweep input of the oscilloscope. In addition, pulses representative of the rate at which the tool moves through the borehole and are integrated and filtered to form a slowly rising ramp voltage which is supplied to the horizontal input of the oscilloscope. Accordingly, the electron beam of the scope generates a raster across the face of the oscilloscope, the intensity of each segment of the raster being dependent upon the strength of the energy reflected from the borehole wall. A photographic film is exposed to this raster and records a picture or record representative of the surface of the borehole wall.

Background of the invention This invention relates to borehole apparatus for investigating a borehole and for reproducing a picture or record representative of the character of the borehole.

In borehole systems of the type involved here, the borehole is scanned through 360 by a rotating transducer means which repetitively emits a burst of high frequency acoustic energy and responds to the reflected energy to provide a voltage signal representative of the intensity of the reflected energy. While investigating through successive 360 scans, the tool is slowly moved through the borehole. For each burst of transmitted energy, the intensity of the reflected energy is dependent upon the character of the borehole receiving the energy. The relative amplitude of the pulse signals developed by the transducer have been found to indicate the presence of anomalies such as holes, cracks, etc., as well as distinguish between hard and soft formations.

The pulse signal developed by the transducer is supplied to the Z axis or intensity input terminal of an oscilloscope to regulate the intensity of the electron beam generated in the scope in accordance with the ampiltude of the signals developed by the transducer. The brightness of the trace appearing on the face of the tube dims and provides a visual indication of the existence of a hole, a crack or a soft spot in a particular portion of the borehole wall, thereby helping to dene the nature of the surrounding formations. In a cased borehole, such indications would provide information as to casing continuity, perforations, etc.

atflt In presently devised systems, the information generated with respect to azimuth and depth often is not sutcient to enable the operator to pinpoint the exact location of variations in the borehole surface. Furthermore, existing synchronizing and signal processing techniques are lacking in reliability and precision, with the result that diiculties are incurred in interpreting the photographs obtained and their usefulness consequently diminished.

Summary of the invention Accordingly, it is an object of the present invention to provide apparatus for scanning the surface of a borehole with acoustic energy and producing a representation thereof which overcomes the above-mentioned disadvantages of the prior art.

It is another object of the present invention to provide apparatus of the above type which provides an automatic correlation between the depth and azimuth of the scanning transducer and the intensity of the reilected energy.

It is still another object of the present invention to provide apparatus of the above type which provides visible depth markings at predetermined intervals on the resulting visual record.

These and other objects of the present invention are accomplished by scanning the surface of the borehole with a rotating transducer which inspects portions of the borehole `with selectively spaced bursts of high frequency acoustic energy and which develops signals corresponding to the intensity of the energy reected from the borehole. These developed signals are then employed to provide a record by modulating the intensity of the electron beam generated by an image reproducing device, e.g. an oscilloscope. A scanning device with a pulse generating network generates a pulse each time the transducer completes one revolution. These pulses are converted into sawtooth voltage pulses and t-hen applied to one of the sweep input terminals, either horizontal or vertical, of the image reproducing device to control thereby the sweep of the beam in one direction across the face of the device. Also provided is a depth information circuit for generating signals representative of the rate at which the transducer is moved within the borehole and for developing another sawtooth voltage signal representative of the distance traveled by the transducer during a given operational cycle. This second pulse is supplied to the other vsweep input terminal of the image reproducing device to control the sweep of the beam in the other direction across the face of the device. To mark the exact depths, a marking circuit is further provided and generates depth information pulses corresponding to selected increments of depth scanned by the transducer means. These pulses are employed to brighten the intensity of the beam for a short duration and vary either the horizontal or vertical sweep of the beam for a short duration to implement the reproduction of dash marks. A recording medium is exposed to the face of the image reproducing device and records a picture of the trace scanned by the scanning beam.

For scanning the surface of an uncased borehole, the pulse generating network includes a rotating magnetometer having transmitter and receiver windings. The magnetometer is responsive to signals supplied to the transmitter windings from an azimuth control circuit and to the earths magnetic eld for developing voltage signals across the receiver Winding. These voltage Signals are coupled back to the azimuth control circuit which compares the signals with a known reference signal and gencrates a Signal each time the magnetometer passes through magnetic North. For use in a cased borehole, switch means are provided on the tool which are actuated once each revolution of the transducer with respect to the tool to generate a reference pulse.

Brief description of the drawings In the drawings:

FIGURE l is a schematic block diagram of an illustrative borehole apparatus arranged according to the present invention;

FIGURE 2 is a schematic block diagram of the signal control and azimuth control circuits of the apparatus of FIGURE l;

FIGURE 3A is a schematic block diagram of certain control panel circuits of the apparatus of FIGURE l;

FIGURE 3B is a schematic block diagram of other certain control panel circuits of the apparatus of FIG- URE l;

FIGURE 4 is a block diagram illustrating the alignment between FIGURES 2, 3A and 3B;

FIGURE 5 is a Wave form display of various signals in time of occurrence for the downhole tool;

FIGURE 6 is a wave form display of various signals in time of occurrence for the surface panel;

FIGURE 7 is a wave form display of various signals in time of occurrence for the signal control circuits shown in FIGURE 2;

FIGURE 8 is a wave form display of various signals in time of occurrence for the circuits shown in FIG- URE 3A;

FIGURE 9 is a wave form display of various signals in time of occurrence for the circuits shown in FIG- URE 3B;

FIGURE 10 is a View of apparatus embodying the present invention as used in a well bore; and

FIGURES 11A and llB are representations of a typical display record obtained from use of the present invention and a cross section of a well bore from which the display is produced.

Description of the preferred embodiment In a representative borehole apparatus arranged according to the invention, as shown in FIGURE 10, a tool 10 is supported in a well borehole 11, which may be cased or open hole, by an armored electrical cable 12 having a suitable number of conductors. The tool 10 includes a motor 18 which rotates a shaft 22. A switch 24, a magnetometer 28 and a directional transducer 32 are coupled to the shaft for rotation therewith. The switch 24 and magnetometer 28 provide an output signal during each revolution of the shaft. The transducer 32 repetitively emits a sonic signal and intercepts its reected return. Electrical circuitry 13 connects the conductors of cable 12 to the various electrical components of the tool. At the earths surface, cable 12 is spooled on the customary winch 14. Slip rings (not shown) or other suitable devices connect the cable conductors to a control panel 15. Signals from the control panel are supplied to an oscilloscope 50 and a camera 68 can obtain pictures of signal displays on the oscilloscope 50 (FIG. llA). At given intervals of cable travel, electrical pulses are supplied to the control panel by an interval pulse circuit 14a.

In FIGURE 11A, a typical record is illustrated. As illustrated, two frames or pictures A and B are successive pictures taken by a camera. Depth numerals are printed on the side frame of the film at 230 and 231. Dots 232 appear in the side frame of the film at 5 intervals. The extreme left and right edges of the traces on the tilm are oriented to the North direction, the remaining directions of East, South and West being disposed intermediate of a North direction. The plane view is a representation of the borehole cylinder. As shown at 233, a fracture in the formation appears as a dark line. As shown in FIGURE 11B, a borehole 234 corresponding to the display of FIG- URE 11A, would have a fracture plane as illustrated by the numeral 235.

Referring now to FIGURE l, in the cable 12, Whose length is suitable for borehole logging operations, includes A-C power conductors 12a and 12b and signal conductors 12C, 12d, 12e, the conductor 12e being shown at ground. A volt A-C power signal is coupled through the conductors 12a and 12b from a pair of input terminals 14 located in a control panel 15 above the borehole to the tool 1t). In the tool, the power signal is coupled to the primary winding 16a of a transformer 16 and to a scanning motor 1S. The secondary winding 16b of the transformer is coupled to a power supply 20, which may be conventional and, accordingly, develops the required negative biasing and positive power D-C voltage signals required for the circuitry in the tool 10.

When energized, the motor 18 drives a shaft 22 at a constant angular velocity which may be, for example, six revolutions per second. A switch 24 is operated by the shaft 22 to momentarily operate a circuit each time the shaft 22 completes one revolution. The switch 24 is connected through conductors illustrated by line 25 to an azimuth control circuit 26 and, in response to the closing of the switch, the circuit produces a signal pulse output. The pulse output of the circuit is particularly useful when logging in a casing is carried out as will be explained more fully hereinafter. Coupled to the shaft 22 is a conventional slip ring assembly 27 which drives a magnetometer probe 28. As will be described in more detail hereinbelow7 the transmitter winding of the magnetometer 28 also receives signals from the azimuth control circuit and, in response to these signals and the presence of an external magnetic field, develops voltage signals across its receiver winding. The receiver winding signals are supplied back to the azimuth control circuit 26. In turn, the circuit 26 generates a pulse 28a (FIG. 5a) each time the magnetometer passes through magnetic North, which may be, for example, six times a second.

Further coupled to the shaft 22 is a second slip ring assembly 39 which drives a sonic transducer 32. Electrically coupled to the transducer is a signal control circuit 34. Control circuit 34 repetitively provides an 0.5 microsecond tire pulse (FIG. 5b) each 50() microseconds, which is supplied through a conventional shaping circuit to the cable 12 as an amplitude shaped To timing signal (FIG. 5c) with a negative characteristic. At a fixed time after each fire pulse, a delayed fire pulse of the control circuit 34 actuates the transducer 32 which emits a burst of energy 32a (FIG. 5d). The To signal precedes the transducer activation by a time sucient to permit control of the effects of the To transmission on the cable so that it does not interfere with the transmission of the returned acoustic energy. The To signal is also designed to provide amplitude reference information.

When the transducer 32 is energized, it generates a two megacycle burst of acoustic energy 32a which is directed toward the borehole wall. Part of the two megacycle burst of acoustic energy is reflected back from the borehole to the transducer 32 which then generates a voltage pulse signal 32b (FIG. 5d) representative ofthe reflected energy. The voltage pulse signal 3217 is sent to the signal control circuit 34. Notably, when the energy emitted from the transducer 32 is directed to a portion of the wall having cracks or holes formed therein, the intensity of the reected energy will be small with respect to energy reected back from a defect-free borehole. It is in this manner that information relative to the condition of the borehole is ascertained. The signal control circuit 34 detects, shapes and amplies the transducer voltage pulse signals and then supplies these signals, referred to herein as Tx signals (FIG. 5e), to the cable 12 with a positive characteristic.

The azimuth pulses, occurring each time the shaft 22 completes one revolution or each time the magnetometer 28 passes through .magnetic North, are supplied to cable conductor 12C. As can be seen, the T0 pulse and the TX pulse as well as the azimuth pulse are transmitted through the cable conductors 12e and 12d, respectively, to the control panel 15.

In the control panel 15, the azimuth pulses are supplied through a conductor 42 to a potentiometer 44 which 5. can be used to adjust the amplitude of the pulses. A slider arm 46 coupled the pulses from the potentiometer 44 to an azimuth sawtooth generator 48 which develops sawtooth voltage signals, each signal having a pulse width of 167 milliseconds (FIG. 6a). A conductor 49 connects the output terminal of the azimuth sawtooth generator 48 to the vertical sweep input terminal 50c of an oscilloscope 50 which is outside the control panel 15. The oscilloscope may be conventional and, accordingly, the operation thereof need not be explained herein. While many different type Oscilloscopes may be employed in the instant invention, one model which has been used with success is the Tektronix 504. Accordingly, for a sawtooth voltage having a pulse width of 167 milliseconds, the electron beam of the scope 50 will complete one vertical sweep in 167 milliseconds.

The T and TX pulses are supplied from the cable conductor 12a to a signal processing circuit 54, timing and control circuits are provided which make certain that only one Tx pulse is processed following the transmission of the T0 pulse. The circuit 54 also provides for the processing of either the T0 pulse or the Tx pulse, but not both, during each operational cycle which lasts for 500 microseconds.

The output of the processing circuit 54 is coupled to a signal amplifier circuit 56 which amplies the signal and supplies it through a conductor 57 to a signal strength monitor meter 58 and also supplies the signal through a conductor 59 to the beam intensity of Z axis input terminal 50b of the oscilloscope 5t) y(FIG. 6b). When recording information relative to the condition of the. borehole wall and only the TX signal is passed by the processing circuit 54, the intensity of the electron beam which scans the face of the tube is dependent upon the intensity of the energy reiiected from the borehole. Where the borehole contains cracks or holes, the intensity of the beam will be low and where the borehole is free from defect, the intensity of the beam will be high.

The length of the borehole is scanned in depth by slowly withdrawing the tool from the borehole. To automatically correlate the depth of the tool 10 with the azimuth and TX information signals, a source of pulses 14a supplies pulses at regular depth intervals to a pulse rate scalar circuit 60 at a xed frequency which is dependent upon the speed at which the scanning tool 10 is pulled up from the borehole. The interval pulses are integrated and filtered in the scalar 60 and supplied to a depth sawtooth generator 62 which generates a slowly rising ramp voltage signal. This ramp voltage signal is supplied to the horizontal sweep control input terminal 50a of the scope 50. After each picture, the ramp voltage is reset, each picture covering a predetermined interval of the borehole. When scanning the borehole in increments of l5 feet, the ramp voltage signal may have a pulse width of 30 seconds, as will be apparent hereinbelow.

Maximum logging speed is determined by the depth interval to be scanned per picture. For the most common interval of l5 feet, a suitable logging speed is 1500 feet per hour or 6 inches per second. At this speed, the l5 feet depth interval requires 3() seconds to log. If the magnetometer 28 is rotated at 6 revolutions per second, the magnetometer will make 180 revolutions during the entire depth interval and, accordingly, the electron beam of the oscilloscope Si) will scan the face of the oscilloscope 180 times in the vertical direction. If logging is carried out at a faster rate, the lines per picture decrease and the resolution suffers. For a logging speed of 1500 feet per hour, the one inch pulses supplied to the pulsed rate scalar are supplied at a frequency of 6 cycles per second as can be understood.

The control panel further includes a marking control network 64 which is responsive to the signals supplied from the pulse rate scalar circuit 60 for generating signals corresponding to selected increments of depth scanned by the transducer 32. Preferably, the network 64 generates signals corresponding to depth increments of 5 feet and supplies these signals through a conductor 66 and a branch conductor 66a to the azimuth sawtooth generator 48 and to the signal amplifier circuit 56, respectively. This respectively implements the reproduction of dash marks and the momentary brightening of the electron beam on the face of the oscilloscope. The marking control network is also responsive to signals developed by the depth sawtooth generator 62 for coupling a signal through a conductor 67 to the printout tubes of a camera 68 mounted on the scope 50. This implements the printout of the depth of the scanned borehole corresponding to the middle of the exposed picture, as will be more fully explained hereinafter. The camera 68 may comprise a Beattie-Coleman camera with a Polaroid film pack. The camera is mounted on the oscilloscope 50 such that each iilm of the lm pack is exposed to the sweep of the electron beam across the face of the oscilloscope 50.

Accordingly, the azimuth and depth scanning voltages supplied to the oscilloscope 50 cause the electron beam of the scope to sweep across the face of the tube and generate a raster similar to that generated in television systems but at a much slower rate. At the same time, the Tx signal is used to modulate the intensity of the electron beam, brightening the beam when the reliection of energy from the wall of the borehole is strong and darkening the beam when the reflection is weak. The exposed hlm of the camera 68 builds up a picture of the surface of the borehole as the beam generates a raster across the face of the scope. At the completion of each complete scan over a depth interval, the lm is removed and a new scan started. The recorded picture represents a section of the borehole which is sliced down the North wall and laid out at. Successive pictures from a continuous picture of the borehole wall. It is noteworthy that resolution in azimuth is not problemsome. For an eight inch diameter hole, a scanning rate of two kilocycles per second and an azimuth scan rate of six revolutions per second, a sample of the wall is taken at intervals of 0.075 inch.

Reference may now be had to FIGURE 2 for a more detailed description of the azimuth control and signal control circuits of the tool 10. The signal control circuit 34 includes a two kilocycle per second (kc./s.) oscillator 70 which may be, for example, a conventional relaxation oscillator circuit, for generating a positive output pulse every 500 microseconds (FIG. 7a). This pulse is applied simultaneously to a single shot circuit 72 and to a single shot gate 74, which respectively control the transducer excitation pulse and transmission of the signals developed by the transducer. In response to the positive pulse applied to its input terminal, the single shot circuit 72 generates a negative pulse which is supplied through a conductor 75 to a pulse generator 76 and through a branch conductor 75a to shaping circuit 78a and an amplifier 78. The width of the pulse generated by the single shot circuit 72 may be, for example, 35 microseconds (FIG. 7b). The shaped and amplied signal from amplifier 73 to cable conductor 12d is a negative pulse To (FIG. 7c) which is shaped in conventional manner to a desired width and choked to minimize the overshoot or positive yback shown by the numeral 78a. The amplitude of the T0 pulse is at the maximum amplification of the amplifier 78.

At the termination of the negative pulse from single shot 72, the trailing or positive going edge drives the pulse generator 76 into operation. Thus the triggering of generator 76 is delayed in time by the width of the pulse output from single shot 72. The pulse generator, which may be of conventional construction, generates a high amplitude level 0.5 microsecond voltage pulse (FIG. 7d) and supplies this pulse through a conductor 80 and a branch conductor 80a to the sonic transducer 32. In

response to the pulse, the transducer 32 generates a burst of two megacycle sonic energy 32a (FIG. 7e) which is directed toward the wall of the borehole. It will be appreciated that the excitation energy for the transmitter is greater than the return energy and, according to the present system, both energies use common channels. To prevent overload to the received signal channel, the branch channel Stib which couples the transducer to the received signal channel is connected to a resistor 82 which couples the pulse from the pulse generator 72 to a variable attenuator circuit 84.

The received signal channel includes a variable attenuator circuit 84, a limiter circuit 36, an emitter follower circuit 88, an operational amplifier and half wave rectifier 94, a pulse stretcher 96, a signal amplifier 98 and a cable driver i). Coupled between the limiter circuit 86 and emitter follower circuit 88 is a clamping circuit 96 and another clamping circuit 92 is coupled between the pulse stretcher circuit 96 and signal amplifier 98. The clamping circuits 90 and 92, in turn, are controlled by the single shot gate 74. Thus, in response to the positive pulse supplied to its input terminal by the oscillator 70, the single shot gate 74 generates a negative pulse (FIG. 7j) which is supplied through a conductor 91 and branch conductors 91a and 911; to the input terminals of the clamping circuits 9G and 92, respectively. The pulse, which may have, for example, a pulse width of 60 microseconds, drives both the clamping circuits 90 and 92 into operation and the output terminals of the circuits are clamped to ground. Accordingly, the output of the limiter circuit S6 and pulse stretcher circuit 96 are clamped to ground thereby precluding the transmission of any signals and specifically excluding the pulse output of pulse generator 76. The pulse width of gate 74 is selected to preclude transmission of any signal effects due to firing of the transducer and preferably, opens the received signal channel just prior to the expected time or arrival of reliected energy.

The two megacycle sonic burst of energy, after traveling through the mud of the borehole, is reflected from the borehole and returns to the transducer 32 at a time dependent upon the size of the borehole and the velocity of the fiuid in the borehole. Just prior to the expected time of arrival of the reflected energy, the clamping circuits 90 and 92 are disabled by termination of the gate 74 pulse. Driven by the reflected wave, the transducer 32 generates a two megacycle signal and supplies this signal to a variable attenuator circuit 84. In the attenuator circuit 84, any pulse signals are attenuated and thereafter supplied to a limiter circuit 86. The limiter circuit 86, which may be, for example, a conventional diode limiter circuit, limits the voltage pulse to a predetermined nominal level, such as, for example, 1.5 volts. The developed signal is selectively attenuated in the variable attenuator circuit 84. Circuit 84 has attenuators which may be, for example, selected to provide gain factors of 1/1, l/3, l/lO or l/3O and can be controlled from the surface by switching downhole relays (not shown). The maximum peak signal obtained in clean oil or Water in a five inch borehole is about 4 volts. Preferably, the attenuator circuit provides a 50 millivolt output signal to avoid overloading.

The signals are therefore transmitted through the limiter circuit 86 and coupled through the emitter follower circuit 88 to the operational amplifier and half wave rectifier circuit 94. The amplifier 94, which may, for example, have a gain of lOO, amplifies the signal and supplies an amplified half wave signal (FIG. 7g) to a pulse stretcher circuit 96. The pulse stretcher circuit 96, which may be conventional, smooths the signal to recover thereby the envelope of the developed signal transient wave and stretches the signal in order to implement better cable transmission, the signal being referred to herein as the Tx signal (FIG. 7h). Following the pulse stretcher circuit 96 is a signal amplifier 93 which amplifies the stretched TX signal. Also connected to the output of the circuit 96 and to the input terminal of the signal amplifier 98 is the clamping circuit 92. As above mentioned, the clamping circuit 92 is driven into conduction for approximately microseconds following the generation of the positive pulse by the oscillator 70. The circuit 92 clamps the output terminal of the pulse stretcher to ground in order to prevent any transients from being transmitted by the amplifier 94, which transients could be caused by the actual tiring of the transducer 32. The amplified Tx signal is then supplied to a cable driver 100 which further amplifies the signal and supplies the signal to the cable conductor 12d.

From the foregoing description, it should be appreciated that the signal control circuit 34 includes in its specific aspects, means for repetitively providing a firing pulse, means for actuating the transducer a predetermined time after the occurrence of a firing pulse, a signal channel connected to the transducer, means for disabling the signal channel for a predetermined time period including the time during which the transducer is actuated, means for transmitting the firing pulse to the output of the circuit 34, and means for transmitting a received signal from the transducer after actuation to the output of the circuit 34.

In order to understand the operation of the azimuth control network 26, it is necessary to understand the operation of the magnetometer probe 28. Accordingly, as shown in FIGURE 2, the magnetometer probe 28 comprises a long thin rectangularly-shaped loop of soft magnetic material with transmitter and receiver windings 28a and 28h, respectively. The transmitter windings 28a is in two parts and is wound around opposite sides of the loop while the receiver winding is wound around the outside of the loop. Without the presence of an external magnetic field, the magnetic field produced in the opposite parts of the transmitter winding 28a by an applied current will cancel each other. Accordingly, a net magnetic field will not result through the receiver and a voltage signal output will not be induced in the winding.

In the presence of an external magnetic field, however, the magnetic material will have a net flux through the receiver winding 2811. In response to an applied sinusoidal signal, the transmitter winding magnetic fiux will begin to rise from zero and the two components will cancel as before, leaving only the unchanging external magnetic field. However, the loop side with the external field in the same direction as the transmitter field will saturate first and the magnetic fiux will no longer increase on this side. The flux on the other side will continue to rise and, no longer being balanced, will induce a voltage in the receiver winding until this side also saturates. The receiver wave form is thus highly distorted and twice the frequency of the transmitted wave form.

The azimuth control network 34 includes, therefore, a drive section for supplying current to the transmitter winding 28a as the magnetometer probe 28 is rotated. The drive section includes a 2O kc./s. oscillator 101 for supplying a series of pulses to a bistable multivibrator circuit 192. In turn, the bistable circuit 102, which may be conventional, supplies a ten kc./s. square wave to a ten kc./s. square wave driver circuit 194. The driver circuit 104, which again may be conventional, supplies a ten kc./s. current signal to the transmitter winding 28a through a pair of conductors to produce magnetic flux in both arms of the winding. Coupled to another output terminal of the driver circuit 104 is a reference signal amplifier 106 which includes a full wave rectifier and 2O kc. filter to provide an amplified 2O kc./s. reference signal in response to the l0 kc./s. signal supplied to its input terminal. The generator 106 supplies the 20 kc./s. reference wave form signal to a phase detector 108.

As the magnetometer 28 rotates, the components of the earths field parallel to the probe cause a 20 kc./s. signal to be generated at the probe receiver winding 28.71.

This signal is supplied through a pair of conductors 110 to the tuned input of a 20 kc./s. signal amplier 112. From the 20 kc./s. amplifier 112, the signal is supplied to another input terminal of a conventional phase detector 108. The phase detector 108 compares the signal produced by the amplifier 112 with the 20 kc./s. reference signal generated by the amplifier 106. When the magnetometer probe 28 is pointed north, the reference signal and the signal developed by the magnetometer- 28 are in phase and the output of the detector is positive. When the probe points south, the reference signal and the developed signal are out-of-phase and the detector output will be negative. If the magnetometer is rotated at an angular velocity of six revolutions per second, a six cycle fundamental sine wave, as Well as a 20 kc./s. signal, will appear at the output terminal of the detector 108.

The output of the phase detector is supplied to a lter 112a which filters out the 20 kc./s. frequency. From the filter 112a, therefore, only the fundamental 6 c.p.s. signal is supplied to the normally closed terminal of a relay contact 113a associated with a relay 113. Energization of the relay 113 is controlled by a switch (not shown) which may be located at the surface and which is closed to implement the energization of the relay 113 only where no magnetic reference is obtainable, such as, when logging in a casing is carried out. With the relay 113 deenergized, therefore, the 6 c.p.s. signal is supplied through the contact 113a to the input terminal of a pulse generator 115. The generator 115 is triggered by the positive cycle of the 6 c.p.s. signal. From the pulse generator 115, a pulse, referred to herein as the azimuth pulse, is supplied to the conductor 12C.

From the foregoing description, with respect to determining a north position, it will be appreciated that this is accomplished by use of a rotating magnetometer which is driven by an oscillating signal generator and a detector compares the magnetometer output with the output of the oscillating signal generator to provide a pulse output in response to the magnetometer output when its probe is pointing north.

When logging in a casing, Where no magnetic field reference is possible, the latching relay 113 is energized by actuation of a surface switch (not shown). Switch contact 113a closes to its normally open position connecting switch 24 to pulse generator 115. The normally open terminal of the contact 113a is connected through the conductor 25 to the switch 24 mounted on the shaft 22 (FIG. l). As above mentioned, the switch 24 closes once each revolution by the shaft 22. The switch is further connected through a conductor 117 and a resistor 118 to a source of positive potential 120. Each time the switch 24 closes momentarily, therefore, a positive pulse is coupled from the conductor 117 through the switch 24 to the conductor 25. Accordingly, when the relay 113 is energized, the positive pulse is coupled through the contact 113g to the input terminal of the pulse` generator 115. In turn, the pulse generator 115 generates a positive pulse, also referred to as an azimuth pulse, which is coupled to conductor 12C. In this manner, the reference is provided to the tool 10 rather than to the magnetic field around the borehole.

As shown in FIGURE 3A, the time space To and Tx pulses are supplied via the conductor 12d to the surface located, signal processing circuit 54. In the circuit 54, the signals are supplied to a potentiometer 122 and, from the potentiometer, the signals are supplied through the slider arm 123 of the potentiometer to a preamplifier 124 which amplifies each of the signals. The gain of the amplifier 124 may be set, for example, to provide a To pulse having an amplitude of 0.2 volt. From the preamplifier 124, the amplified To and Tx signals are then supplied through a conductor 125 and its branch conductors 125a, 125b and 125C to an ampli- 10 fier 126, a rheostat 127 and a second amplilier 128, respectively.

Processing circuit 54 can selectively process either T0 or TX pulses to the signal strength meter 58 and recording means but not both at one time. Both To and Tx are used, however, in obtaining a recording of the TX signals. Considering first the processing of the To pulse, initially, the To pulse is amplified by the amplifier 126 and coupled to a Schmitt trigger circuit 130, the circuit 130 constituting a To detector. In response to the T0 pulse exceeding a given negative amplitude at its input terminal (FIG. 8a), the circuit 130 generates a positive pulse having a predetermined pulse width (FIG. 8b). 'Ihis pulse is connected through a conductor 132 to a single shot multivibrator circuit 134 and through a conductor 135 to one input terminal 136a of a gate 136. The single shot circuit 134 is responsive to the leading edge of the positive pulse and emits a 400 microsecond positive output pulse (FIG. 8c). The single shot circuit 134, once triggered, is insensitive to further triggering until after resetting 400 microseconds later, as is understood in the art. It can be seen that this circuit insensitivity reduces the possibility of noise pulses, and the like, triggering the following stages of the signal processing circuit 54 and simulating the generation of more than one To pulse each operational cycle.

Connected to the output terminal of the single shot circuit 134 is an adjustable single shot multivibrator circuit 138 which is triggered by the leading edge of the 400 microsecond pulse. When triggered, the single shot circuit 138 generates a positive pulse (FIG. 8d) which may have, for example, a pulse width adjustable between 50 to 400 microseconds. A conductor 14() and its branch conductors 140a and 140b couple this pulse to one input terminal of an AND gate 142 and to the set input terminal of a Hip-flop circuit 144, respectively. The flip-flop 144 is driven into the l state by the positive going edge of the pulse from single shot 138 (FIG. 8c) and a signal is connected from the ip-op 144 by conductor 140C to the other input terminal of the AND gate 142. At the end of the single shot 138 pulse, both inputs to the AND gate 142 are down to enable the gate (FIG. 8f). The output terminal of the AND gate is connected to the control input terminal of the Schmitt trigger circuit 146 and when AND gate 142 is enabled, circuit 146 is enabled. The Schmitt trigger circuit 146 constitutes a TX detector circuit.

With respect to the To pulse therefor, the circuit 15, detects the amplitude of the T0 pulse and provides a pulse output with a predetermined width to a gate 136 which, as hereinafter will be more fully explained, can be used to provide indication of the To amplitude. The pulse output also, after an adjustable time delay period, conditions or opens the Tx detector channel by enabling circuit 146.

As above-mentioned, both the To and TX pulses are supplied through the conductor 125 and the branch conductor 125b to the rheostat 127. Coupled to the rheostat 127 through the center arm thereof is an amplifier 148. The rheostat 127 can be adjusted to detect TX pulses by amplitude. In other Words, at the low end of the rheostat, few pulses will be passed while at the high setting of the rheotat most Tx pulses will be passed to circuit 146. Accordingly, the TX signal is amplified by the arnplifier 148 and supplied to the input terminal of the Schmitt trigger circuit 146. The amplifier TX signal drives the Schmitt trigger circuit into operation only if the AND .gate 142 has been enabled, as above-mentioned.

When the Schmitt trigger circuit 146 is triggered into operation, the circuit generates a positive pulse (FIG. 8g) and supplies this pulse to the reset input terminal of the iiip-flop 144 and to one input terminal 150a of a gate 150. The trailing edge of the circuit 146 pulse resets the flip-Hop 144 to the 0 state and the AND gate 142 is disabled and, in turn, the Schmitt trigger circuit 146 is disabled. Accordingly, it can be seen that only one TX signal will be detected each operational cycle and will not be detected again until the next detection of the To signal.

As above mentioned, the spaced T and TX pulses are also supplied through the conductor 125 and the branch conductor 125e to the amplifier 128. The amplier 128 amplies both signals and supplies both signals to one input terminal 152a of a gate 152. The gate 152 passes either the T0 or the TX signal, but not both, as will be apparent hereinbelow. The output signals from both the T0 detector 130 and the TX detector 146 are, as mentioned above, connected to one input terminal 136a and 150a of the gates 136 and 150, respectively. The other input terminals 136b and 150]: of these gates are connected to the closed and open terminals, respectively, of a manually operated switch 154. The contact arm of the switch 154 is connected to ground.

When the input terminal 1501: of the gate is connected to ground through the switch 154, the gate will be enabled by the positive pulse supplied to its input terminal 150a from the Schmitt trigger circuit 146 and will pass this pulse. On the other hand, when the switch 154 couples the input terminal 136b of the `gate 136 to ground, the gate will pass the To signal Supplied from the Schmitt trigger circuit 130 and the gate 150 will be disabled. The output terminals of the gates 136 and 150 are connected together and to the input terminal of a single shot circuit 156. In response to either the T0 or the TX signal, the circuit 156 generates a positive pulse having a predetermined pulse width (FIG. 811 or FIG. 8i). This signal is coupled through a conductor 157 to the other input terminal of the gate 152 and enables the gate for a predetermined time. Accordingly, the gate will pass either the To signal or the TX signal, but not both depending upon which of the gates 136 or 150 is enabled. When providing amplitude reference information, the gate 136 will be enabled and the To signal will be passed by the gate 152. When scanning the borehole wall, the gate 150 will be enabled and only the TX signal will be passed by the gate 152.

The output of the gate 152 is coupled to a polarity selection circuit 158 which is intended to provide only negative pulse outputs. In the circuit are rheostats 160 and 162 which are connected to the terminals of a manually Operated switch 164. Switch 164 is mechanically ganged to switch 154. In the switch position illustrated, TX signals which have a positive characteristic are processed. Thus, the effect of circuit 158 and rheostat 160 are to invert the signal to a negative characteristic. When a To pulse is being processed, the To pulse is passed through circuit 158 and rheostat 162 without inversion.

From the switch 164, either the To or the Tx pulse is supplied to the signal amplifier circuit 56. The amplifier circuit 56 includes an operational amplifier 166, which may have, for example, a gain of 100, for amplifying either the transmitted To or the transmitted TX pulse. From the amplier 166, the transmitted signal is supplied through a conductor 167 and its branch conductors 1670, 167/J and 167C to the input terminal of an emitter follower circuit 168, the intensity input of the oscilloscope 50, the conductor 16'7b being an extension of the conductor 59 (FIG. l) and to the output terminal of a common emitter amplifier 170, respectively. From the common emitter amplifier 16S, the transmitted signal is supplied to the signal strength monitor meter 58 which measures and provides a visual indication of the amplitude of the transmitted signal.

As above mentioned, to provide amplitude reference information, the T0 signal is transmitted to the meter 58 and while not necessary can also be supplied to the Z axis or scope intensity input terminal 50h of the oscilloscope 50. During the actual scanning of the borehole wall, the T,l signal is transmitted to both the meter 58 and to the intensity input terminal 50h of the oscilloscope. W'here substantially all the sonic energy is reected back from the Wall of the bore hole, the amplitudes of the developed Tx signal will be high, the scanning beam will be bright and there will be a substantial deflection of the indicator arm of the meter 58. Meter 58 has a long time constant so that average indications are obtained. Where holes or cracks in the wall are scanned, the TX signal will have a small amplitude, the beam of the scope will be dim and there will be only minimal deflection of the arm of the meter 53. As will be explained in detail hereinafter, the common emitter amplier 170 is driven by a five-foot marker pulse developed by the marking control network 64 (FIG. l). When triggered, the amplifier 170 supplies an inverted and amplified marking signal to the input terminal Sb of the oscilloscope via conductors 167C and 167b. A resistor 167:2' prevents the marking signal from having an effect on the emitter follower circuit 168 and meter 58. Accordingly, there will be a brightening of the scanning beam in the oscilloscope to record the scanning of a depth increment of tive feet.

The output of the delay circuit 138 is also connected to a capacitor and resistor circuit 138a to provide positive and negative spike pulses at the beginning and end of the delay circuit pulse. Circuit 139a is connected by a test switch 139 to the beam intensity control of the scope. When switch 139 is closed, the trailing negative spike pulse causes a momentary brightening of the beam and hence an indication of the time relative to the arrival of a TX pulse. The output of single shot circuit 156 is also coupled via a resistor 156e to switch 139. The effect of applying the output of circuit 156 to the beam intensity is to brighten the TX signal occurring during the output to ascertain which part of the Tx pulse is being detected.

As shown in FIGURE 3B, the azimuth pulses are supplied from the input conductor 12C to a potentiometer 44. Voltage regulated azimuth signals are thereupon coupled through the center arm 46 of the potentiometer to an input terminal of the sawtooth generator 48. As above mentioned, the circuit 48 develops a sawtooth voltage signal having a pulse width of 167 milliseconds and couples this signal through the conductor 49 to the vertical sweep inpust terminal 50a of the oscilloscope 50` (FIG. 1). Accordingly, the vertical sweep by the scanning beam of the oscilloscope 50 is controlled by this sawtooth voltage signal and the beam will complete one Vertical sweep every 167 milliseconds.

As above mentioned, the length of the borehole is investigated by slowly withdrawing the tool 10 from the borehole and to correlate the depth of the tool 10 with the azimuth and TX signals, a source of pulses 14a supplies pulses at 1l intervals to the pulse rate scalar circuit 60 (FIG. l). Referring again to FIGURE 3B, the pulse rate scalar circuit 60 comprises a Schmitt trigger circuit for generating a sharp positive pulse each time the circuit is triggered by a 1 interval pulse (FIG. 9a). From the circuit 190, each pulse (FIG. 9b) is coupled through a conductor 191 to a pulse doubler circuit 192 and to a one-foot binary counter 193.

The pulse doubler circuit 192 develops square wave voltage signals (FIG. 9c) having transitions at 1/2" intervals. From the pulse doubler circuit 192, the J/2" pulses are supplied to a complementary hip-flop 194 included within the depth sawtooth generator 62 (FIG. 1). The flip-flop 194 may be conventional, and, accordingly, provides complementary output voltage signals (FIG. 9d and FIG. 9e) in response to each 1/2" pulse supplied to its input terminal. Specically, the opposite output terminals of the flip-flop 194 provide positive and negative voltage levels for each transition of the square wave signal generated by the pulse doubler circuit 192.

The opposite output terminals of the flip-op 194 are connected to the input terminals of an OR circuit 195 which provides a positive pulse output (FIG. 9]) each time a positive pulse is applied to either of its input terminals. Accordingly, the OR cricuit 195 provides a positive pulse output for each transition of the square wave signal supplied to the input terminal of the complementary nip-flop 194. From the OR circuit 195, the l positive pulses are supplied to a frequency divider circuit 196 which is capable of dividing by one, two, three, six or twelve to provide -1/2", l, l1/2", 3 or 6" pulses, respectively. The extent of the division is dependent upon the length of borehole to be investigated during any given operational cycle.

An operational cycle can be accomplished over various length intervals along the borehole and the present system is based on using 120 pulses as a common base. Therefore, the following will apply:

Interval:

5 feet-120 pulses at 1/2 intervals l feet- 120 pulses at 1 "intervals l feet- 120 pulses at 11/2 intervals 30 feet-120 pulses at 3 intervals 60 feet-120 pulses at 6 intervals The frequency divider circuit 19'6 is, therefore, selectively enabled by a predetermined voltage level appearing at its input terminals 196a, 19613, 196e, 196d and 196e which respectively correspond to 5 feet, 10 feet, 15 feet, 3() feet and 60 feet.

From the frequency divider network 196, the pulses are supplied to the set input terminal of a binary counter 197. The counter 197 comprises seven stages and counts to 120. When the number 120 is accumulated in the counter, the positive voltage levels appear at the output terminals of the last four stages in the counter and these positive voltages are supplied to a 120 count AND gate 198. The output terminal of the gate 198 is coupled back to the reset input terminal of the binary counter 197 and when driven into operation, the gate 198 resets the binary counter 197. Also coupled to the 120 count AND gate 198 is a status indicator and control unit 200. The status indicator and control unit 200 is provided with lamps, switches and the like for controlling the operation of the borehole apparatus of the present invention. For example, by the suitable depression of the switches of the panel 200, the counter 197 may be reset at any time, the depth control voltage levels supplied to the frequency divider circuit 194 may be changed and the counter 197 may be disabled at any time.

Each stage of the binary counter 197 is further coupled to a binary-to-analog converter 202 which converts the binary number in the counter 197 to an analog voltage. The converter 202, which may be conventional, is arranged to develop a ramp voltage signal as the count is accumulated in the binary counter 197. From the converter 202, the ramp voltage is supplied through the conductor 62a to the horizontal sweep input terminal 50c of the oscilloscope 50. Accordingly, each horizontal sweep by the scanning beam of the scope 50 will correspond to a scan of the borehole wall in a particular depth, which may he 5, 10, 15, 30 or 60 feet.

Further connected to the last or seventh stage of the binary counter 197 through a conductor 203 is a 64 count detector 204 which is included within the marking control network 64. As above mentioned, the 1" interval pulses detected by the Schmitt trigger circuit 190 are supplied through the conductor 191 to the pulse doubler circuit 192 and to the one-foot binary counter 193. The binary conuter 193 may be, for example, a four-stage binary counter with feedback from the last two stages which is used to reset the counter at the count of 12. Accordingly, the 1 interval pulses are converted thereby into one-foot pulses. From the counter 193, the onefoot pulses are supplied to a single shot amplifier 206 which generators a 180 millisecond pulse. This pulse is applied to the stepping circuit of an odometer 208 which may be of conventional construction and, accordingly, need not be described herein. The odometer 208 is included within the control panel and counts the number of one-foot pulses supplied to its input terminal by the single shot circuit 206.

The 0 and 5 units of the units decade of the odometer 208 are connected through a pair of conductors 210 and 212 to a pair of input terminals of a five-foot gate circuit 214 located in the marking control network 64. The gate 214, which may be, for example, on OR circuit, provides an output signal whenever a ground signal is supplied to either of its input terminals. The conductors 210 and 212 carry ground signals from the units decade of the odometer 208 whenever the odometer registers a 0 or a 5 in the units decade. When enabled, the gate circuit 214 supplies signals to the set input terminal of a tive-foot flip-flop circuit 216. The iiip-ilop 216 is driven thereby into the 1 state. Coupled to the set output terminal of the tive-foot flip-flop circuit 216 is one input terminal 218a of a NAND gate 218. When the ip-op is driven into the l state, the voltage level at the set output terminal of the flip-flop 216 tends to enable the gate 218.

The other input terminal 218b of the NAND gate is coupled to the output terminal of the azimuth sawtooth generator 48 through a conductor 219 and the conductor 49. When the sawtooth voltage signal generated by the sawtooth generator 48 falls sharply during reset, the negative going pulse enables the NAND gate which then produces a positive pulse. This positive pulse is supplied to the input terminal of a single shot circuit 220 and t0 the reset terminal of the five-foot flip-nop circuit 216. The flip-flop 216 is reset to the 0' state by the positive pulse.

The single shot circuit 220 generates a marking pulse having a predetermined pulse width and couples the pulse to the sawtooth generator 48. The sawtooth voltage signal generated by the generator 48 is clamped by the applied marking pulse to a reset level which may be, for example, one volt less than the ordinary reset level. Accordingly, the scanning beam of the scope 50 will be momentarily deflected in the vertical direction and a dash mark will be traced on the face of the oscilloscope 50 to indicate the scanning of a ve-foot depth increment. The marking pulse is also coupled through the conductor 66a to the base of the common emitter amplifier 170 located in the signal amplifier card 56 (FIG. 3A). The amplifier inverts and ampliiies the pulse and then supplies the pulse through the conductor 167e and the conductor 167 to the intensity input terminal 50h of the oscilloscope. Accordingly, the dash mark will appear brighter than the remaining portions of the trace.

As above-mentioned, the seventh stage of the counter 197 is coupled through the conductor 203 to the 64 count detector 204 of the marking control network 64. The seventh stage is set or driven into the l state at the 64th count and remains in the l state for the remainder'of the borehole scanning cycle or until the count reaches 120. On the 64th count, the scanning beam of the oscilloscope 50 has completed one-half its horizontal trace, as is understood. The pulse generated by the transition of the last stage of the counter 197 from the 0 to the 1 state drives the 64 count detector, which may, for example, drive a Schmitt trigger circuit, into operation. In turn, the detector supplies a pulse to a single shot circuit 22 which then generates a millisecond pulse. This pulse energizes a numerical readout control relay 224 having associated contacts (not shown) which connect 200 volts to the numerical readout tubes 68a of the camera 68. The tubes are coupled to the odometer 208 and flash whatever nurnber appears in the odometer 208. In this manner, the tubes 68a printout on the exposed lm the depth corresponding to the middle of the picture.

In operation, therefore, the wall of a borehole is rotationally scanned by a tool 10 which includes a two megacycle transducer 32 and a magnetometer probe 28. While a two megacycle transducer 32 is used, a frequency betweeen one and two magacycles is generally preferred. The transducer 32 is supplied with high frequency voltage pulses every 500 microseconds from the signal control netl work 34 while the magnetometer probe 28 is supplied with a kc./s. signal from the azimuth control network 26. Prior to the triggering of the transducer 32 with the high frequency pulses, the signal control circuit 34 generates a To pulse which is employed for both timing control and amplitude reference information in the control panel l5.

The transducer 32 develops voltage signals which are representative of the intensity of the high frequency energy reflected back from the wall of the borehole and supplies these signals back to the signal control network 34 which develops TX signals. Thereupon, these TX signals are supplied to the control panel 15. The magnetometer probe 28 develops 2O `lio/s. signals and supplies these signals back to the azimuth control circuit 25. In the azimuth control circuit signals are compared with a reference 2O kc./s. signal and an azimuth signal is generated by the circuit 26 each time the magnetometer probe 28 passes through magnetic north which may be, for example, six times a second.

In the control panel, both the T0 and Tx pulses are supplied to the signal gate circuit 54 which amplies and supplies as an output signal either the To or the TX signal each Operational cycle. Timing control circuitry is provided in the circuit 54 to prevent the generation of more than one signal each operational cycle. Where amplitude reference information is required, only the To signal is transmitted and where information concerning the surface ofthe borehole wall is required, only the TX signal is transmitted. From the signal gate circuit 54 one of the signals is supplied to the signal amplifier circuit 56 which amplies the transmitted signal and supplies a signal to the meter 58 and to the intensity input terminal Sb of the oscilloscope 50.

Also in the control panel 15 the azimuth pulses are supplied across the potentiometer i4 and then to the sawtooth generator 48. The sawtooth generator 4S develops a sawtooth voltage signal having a pulse width equal to the spacing between successive azimuth pulses. Where azimuth pulses are generated six times a second, the sawtooth voltage signal generated by the sawtooth generator 43 has a pulse width of 167 milliseconds. This puise is then supplied through the conductor 49 through the vertical sweep 50a of the oscilloscope 50 to drive thereby a scanning beam of the scope in the vertical direction.

To correlate depth information with the developed Tx and azimuth pulses, l pulses are supplied to the pulse rate scalar circuit 60 and the control panel 15. The scalar circuit 6() develops pulses which are representative of the rate at which the scanning tool 10 is withdrawn from the yborehole and these signals are integrated and reflected to form a slowly rising ramp voltage by the depth sawtooth generator 62. The generator 62 supplies this ramp voltage to the horizontal sweep input terminal 50a of the oscilloscope and the beam of the scope is driven at a slow rate across the face of the tube. The electron beam of the scope, therefore, generates a raster across the face of the oscilloscope with the intensity of each segment of the raster being dependent upon the strength of the developed TX signal.

Also provided is the marking control circuit 64 which develops pulses corresponding to the scanning of a fivefoot increment of the borehole. These pulses are supplied both to the azimuth sawtooth generator 48 and to the signal amplifier card 56 such that the scanning beam of the scope is momentarily deflected in the vertical direction and a brightened dash mark will be traced on the face of the oscilloscope 50. Furthermore, the seventh stage cf the binary counter 197 of the generator 62 is coupled to the marking control circuit 64 and implements the triggering of the numerical readout tubes in the camera 68. The tubes 68a print out the depth of the scanned borehole corresponding to the middle of the picture.

Although the invention has been described herein with reference to specific embodiments, many modifications and variations therein will readily occur to those skilled in the art. Accordingly. all such variations and modifications are included within the intended scope of the invention as defined by the following claims.

What is claimed is:

1. A well logging tool comprising transceiver means for probing materials defining a Well bore with repetitive pulses of energy and for receiving energy reliected from said materials, means for rotating said transceiver means at a speed such that a number of repetitive pulses can be emitted during each revolution of said transceiver means; means for providing a first electrical pulse having a predetermined amplitude characteristic for each pulse of energy; said transceiver means providing second electrical signals in response to received energy; a receiver signal channel; a common output channel connected to said channeland said first electrical pulse means and including variable attenuation means; means operative at the time of occurrence of Said first electrical pulse for disabling said receiver channel until a time just prior to the time of arrival of a reflected pulse of energy.

2. The apparatus of claim 1 wherein said first electrical pulse has a predetermined amplitude characteristic.

3. The apparatus of claim 1 wherein said common output channel includes variable attenuation means.

4. Means for processing electrical signals received from a rotatable well bore tool which provides time spaced signals representative of the occurrence of transmitter and receiver signals during the rotation of the tool comprising: a signal processing circuit adapted for processing receiver signals only when a transmitter signal precedes a receiver signal; means for selectively conditioning said processing circuit to process only a transmitter signal.

5. A well logging tool comprising: transceiver means for probing material surrounding the well tool with repetitive pulses of energy and for receiving energy reflected from said materials; means for rotating said transceiver means at a speed such that a number of repetitive pulses can be emitted during each revolution of said transceiver means; means for energizing the transceiver means to emit energy and for providing a first electrical pulse for each pulse of energy; said transceiver means providing second electrical signals in response to received energy; a receiver signal channel including variable attenuation means responsive to the rst electrical pulses and to the second electrical signals; a common input channel connecting said receiver channel and said energizing means; means operative at the time of occurrence of said first electrical pulse for disabling said receiver channel until a time just prior to the time of arrival of a reected pulse of energy.

6. The apparatus of claim 5 wherein said receiver channel further includes amplitude limiting means for limiting the amplitudes of the first electrical pulses and second electrical signals supplied thereto.

7. Apparatus for use in a well bore to provide a representation correlatable with the wall surface of a well bore comprising: transducer means adapted for movement along a borehole and operable to provide at discrete angles about the longitudinal axis of the apparatus repetitive pulses of high frequency energy and develop signals corresponding to the time of such bursts and the energy reflected from a borehole; means for providing information signals correlatable to the reiiected energy; means for generating at least one azimuth pulse for each 360 scan of the wall surface by the transducer means; means for generating pulses whose repetition rate is representative of the rate at which the transducer means is moved along the length of the borehole; image display means having vertical and horizontal sweep means, and beam intensity control means; means responsive to the occurrence of a signal representative of the time of a burst of energy and the suceeding information signal for supplying one amplitude signal for each operational cycle to the beam intensity control means of the image display means to thereby modulate the intensity of the beam in accordance with the amplitude of said one signal; means responsive to each azimuth pulse for developing a control signal and supplying the control signal to one of the sweep means to control thereby the sweep of the beam in one direction across the display means; and digital converter means responsive to the pulses whose repetition rate is representative of the rate at which the transducer means is moved along the length of the borehole for developing an analog ramp Voltage signal and Supplying the signal to the other of said sweep means to control thereby the sweep of the beam in a second direction across the display means.

8. Apparatus according to claim 7 wherein the digital converter means comprises counter means for counting the rate pluses and digital-to-analog converter means coupled to said counter means.

9. Apparatus vaccording to claim 8 wherein the digital converter means further comprises frequency divider means responsive to the pulses representative of the rate at which the transducer means is moved along the length of the borehole for providing second pulses having frequencies dependent upon the depth of the borehole to be scanned and supplying the second pulses to the counter means.

10. Apparatus according to claim 9 further comprising camera means exposed to the image display means and having numerical printout tubes, odometer means connected to the printout tubes and responsive to the rate pulses for registering the depth of the transducer means and means coupled to the counter means for selectively triggering the numerical printout tubes to implement thereby the printout onto the camera means of the depth registered in the odometer means.

11. Apparatus according to claim 10 further cornprising detection means operatively coupled to the odometer means for developing pulses indicative of preselected depths registered by the odometer means and for adding said pulses to the azimuth control signal and for supplying said pulses to the beam intensity control means of the image display means.

12. A well logging system comprising: a lo-gging tool adapted for movement through a well bore having transceiver means for probing materials defining a well bore with repetitive pulses of energy and for receiving energy reflected from said materials, means for rotating said transceiver means at a speed such that a number of repetitive pulses can be emitted during each revolution of said transceiver means, means for energizing the transceiver means to emit energy and for providing a rst electrical signal for each pulse of high frequency energy, said transceiver means providing second electrical signals in response to received energy, a receiver signal channel a common input channel connecting the receiver channel and the energizing means, a common output channel connected to said receiver channel and said first electrical pulse means, means operative at the time of occurrence of said first electrical signal for disabling said receiver channel until a time just prior to the time of arrival of a reflected energy pulse, and means for generating a third electrical signal related to a 360 revolution of the transceiver means; and a surface located control panel comprising means for processing said first and second signals to provide an output signal representative of said second signal when both rst and second signals occur, means for sequentially recording data representing the output signal representative of the second signal through each 360 of revolution of the transceiver means, and means for applying the third electrical signal to the `recording means to indicate the relationship between the sequentially recorded data and the third electrical signal.

13. The apparatus of claim 12 wherein said recording data means includes an oscilloscope and each sequence of recording data is generally horizontally displayed on said oscilloscope, and means are provided to correlate movement of the logging tool through a Well bore in relation to said recording data means for separately recording each sequence one from the other.

14. A well logging system comprising: a logging tool adapted for movement through a well =bore having a transceiver means for probing materials dening a well bore with repetitive pulses of energy and for receiving energy reected from said materials, means for rotating said transceiver means at a speed such that a number of repetitive pulses can be emitted during each revolution of said transceiver means, means for energizing the transceiver means to emit energy and for providing a first electrical signal for each pulse of high frequency energy, said transceiver means providing second electrical signals in response to received energy, a receiver signal channel, means operative at the time of occurrence of the said rst electrical signal for disabling Said receiver channel until a time just prior to the time of arrival of a reected energy pulse, and means for generating a third electrical .signal related to a 360 revolution of the transceiver means; and a surface located control panel comprising means for processing said first and second signals to provide an output signal representative of said second signal when both rst and second signals occur, recording data means including image display means having first and second sweep control means and beam intensity control means responsive to the output signal representative of the second signals, means responsive to the third electrical signal for developing a rst control signal and supplying the control signal to the first sweep control means, means for generating pulses whose repetitive rate is representative of the rate at which the transceiver means is moved along a length of the borehole and means responsive to the rate pulses for developing a second control signal and supplying the second control signals to the second sweep control means.

15. Apparatus according to claim 14 wherein the recording data means further comprises a photographic medium exposed to the display means for -building up a picture of the borehole wall as the beam scans the face of the display means.

16. Apparatus according to claim 15 wherein the recording data means further comprises camera means having numerical printout tubes, odometer means connected to the printout tubes and responsive to the rate pulses for registering the depth of the transceiver means, and means responsive to the second control signal for triggering the numerical printout tubes to thereby implement the printout onto the photographic medium of the depth registered in the odometer means.

17. Apparatus according to claim 14 further comprising marking control network means responsive to the rate pulses for generating depth information pulses corresponding to selected increments of depth scanned by the transceiver means.

18. Apparatus according to claim 17 wherein the marking control means further includes means responsive to the depth information pulses for supplying the signals to the beam intensity control means of the display means to thereby momentarily increase the intensity of the beam and means for supplying the depth information signals to the first sweep control means to thereby implement the momentary departure of the beam from its normal sweep across the face of the display means.

19. Apparatus according to claim 12 wherein the means responsive to the third electrical signal comprises azimuth sawtooth generator means for generating a sawtooth voltage signal and for supplying the sawtooth voltage signal to a rst sweep control means of the display means to control thereby the sweep of the beam in one direction across the face of the display means.

20. Apparatus according to claim 14 wherein the means responsive to the rate pulses comprises means responsive to the pulses for providing second pulses at a frequency dependent upon the depth increment of the borehole to be scanned, counter means for accumulating a predetermined count of the signals, and binary-to-analog converter means responsive to the counter means as the count is accumulated for developing a ramp voltage and supplying the voltage to the second sweep control means of the display means to control thereby the sweep of the beam in a second direction across the face of the display means.

21. Apparatus for automatically correlating the depth of a logging tool adapted for movement through a well bore with borehole information signals developed by the logging tool comprising: pulse source means for generating pulses representative of the rate at which the logging tool is moved through the Well bore, means responsive to the pulses for providing a fixed number of second pulses at a frequency dependent upon the depth increment of the borehole to be scanned, and converter means responsive to the fixed number of said second pulses for developing a rising ramp voltage signal having a pulse width corresponding to the time it takes the logging tool to scan the particular borehole depth increment.

22. Apparatus according to claim 21 wherein the means for providingT a fixed number of second pulses comprises frequency divider means responsive to the pulses for reducing the frequency of the fixed number of pulses in accordance with the particular borehole depth increment to be scanned and counter means responsive to said fixed number of reduced frequency pulses for accumulating the fixed number of reduced frequency pulses.

23. In a well logging system, the combination comprising: a Well logging tool having means for repetitively emitting and receiving energy in a media surrounding said well tool, means for rotating said energy emitting and receiving means so that energy will be directed at various circumferential portions of a well bore, means for producing a transmitted energy sync pulse representative of the time that said energy is emitted, means for producing a received energy signal pulse representative of the emitted energy which is returned to said well tool, and means for transmitting said sync and signal pulses to the surface of the earth, said sync and received signal pulses being of opposite polarity; means for detecting said transmitted sync pulses and generating a first output pulse Whenever one of said transmitted pulses exceeds a given amplitude level of the polarity corresponding to the polarity of said sync pulses; means responsive to said first output pulse for producing an enabling pulse during a selected time interval corresponding to the time interval relative to a sync pulse during which a received signal pulse is expected; memorizing means responsive to said enabling pulse and a second output pulse for memorizing the relative time sequence of said sync and signal pulses; means coupled to said memorizing means and responsive to said signal pulses for producing said second output pulse Whenever said signal pulse exceeds a given amplitude level and is immediately preceded by a sync pulse, whereby said first and second output pulses will accurately correspond to the transmitted sync and signal pulses.

24. The apparatus of claim 23 wherein said memorizing means comprises a bistable storage means for memorizing which of said enabling pulse or said second output pulse occurred last and generating a third output signal if said sync pulse occurred last, and wherein said means for producing said second output pulse includes means responsive to the time coincidence of said enabling pulse and said third output signal and the appearance of a transmitted signal pulse for producing said second output pulse.

25. A Well logging system, comprising: a Well logging tool having means for repetitively emitting and receiving energy in a media surrounding said well tool, means for producing a transmitted energy sync pulse representative of the time that said energy is emitted, means for producing a received energy signal pulse representative of the emitted energy which is returned to said well tool, and means for transmitting said sync and signal pulses to the surface of the earth, said sync and received signal pulses being of opposite polarity; means for detecting said transmitted sync pulses and generating a first output pulse Whenever one of said transmitted pulses exceeds a given amplitude level of the polarity corresponding to the polarity of said sync pulses; means responsive to said first output pulse for producing an enabling pulse during a selected time interval corresponding to the time interval relative to a sync pulse during which a received signal pulse is expected; means responsive to said signal and enabling pulses for producing a second output pulse whenever said signal pulse exceeds a given amplitude level and is immediately preceded by a sync pulse; selectable gating means responsive to a selected one of said first or second output pulses for passing a selected one of the sync or signal pulses to a utilization device.

26. In a well logging system of the type wherein energy is repetitively emitted and received in a media surrounding a well tool to produce received energy signal pulses representative of the received energy and transmitted energy sync pulses representative of the time that said energy is emitted, for transmission to the Surface 0f the earth in opposite polarity form, the combination comprising: means for detecting said transmitted sync pulses and generating a first output pulse whenever one of said transmitted pulses exceed a given amplitude level of the polarity corresponding to the polarity of said sync pulses; means responsive to said rst output pulse for producing an enabling pulse during a selected time interval corresponding to the time interval relative to a sync pulse during which a received signal pulse is expected; means responsive to said signal and enabling pulses for producing a second output pulse Whenever said signal pulse exceeds a given amplitude level and is immediately preceded by a sync pulse; selectable gating means responsive to a selected one of said first or second output pulses for passing a selected one of the sync or signal pulses to a utilization device.

References Cited UNITED STATES PATENTS 2,631,270 3/1953 Goble 340-18 2,825,044 2/ 1958 Peterson.

2,968,724 1/1961 Clark 340-18 3,065,405 ll/l962 Jarrett 340-18 3,170,136 2/1965 Howes 340-18 3,252,131 5/1966 Vogel.

3,292,034 12/1966 Braaten 315-19 3,340,501 9/1967 Georgi et al.

3,369,626 2/ 1968 Zemanek.

2,910,133 l0/l959 Hudson et al.

3,011,339 12/1961 Furon 73-67.9 3,021,706 2/1962 Cook et al 73-67.8 3,243,009 3/1966 Vogel.

3,350,924 11/1967 King 73-67.9

RICHARD A. FARLEY, Primary Examiner C. E. WANDS, Assistant Examiner 

